Descriptions

The acanthocephalan Echinorhynchus lageniformis Ekbaum,
1938, is a common intestinal parasite of the starry flounder, Platichthys
stellatus (Pallas), of Yaquina Bay, Lincoln Co., Oregon. Three
hundred and sixty-one flounders were examined and 146 (40.5 percent)
were found to harbor infections of E. lageniformis.
Cystacanths of E. lageniformis were found encysted in the
body cavity of the starry flounder; this is probably the result of the
fish feeding on larval infections not yet mature enough to attach to
the intestinal mucosa.
As the size of the flounder increased, the percent infection
decreased. The smaller fish with the higher incidence of infection
were found to be of the size range that ate amphipods, which may be
the intermediate host, as the main part of their diet. The older fish
do not feed on amphipods.
A correlation could not be found between the sex of the starry
flounder and the incidence and degree of parasitism.
A peak of adult worms was found in April, 1966 - 198 mature
females as compared to a low of 30 mature females in December,
1965. This indicates a seasonal periodicity in the E. lageniformis
population of Yaquina Bay. Possible explanations for this seasonal
occurrence were discussed.
It is postulated that E. lageniformis lives in its final host for
about a year. The one-year-old plus fish were found to have a high
incidence of infection, whereas the two-year plus fish had a low incidence
of infection.
Twenty-six percent of the worms collected were males and
74 percent were females. Of the 146 infections, 74 were unisexual
and 72 were mixed (containing both sexes). In April, 1966, the
percent infection was the highest - when there were 20 mixed infections
and two unisexual infections. This indicates that all the
females have a good chance of being fertilized.
The starry flounder intestine reacts to E. lageniformis at
the point of attachment. It was observed that the larger the worm,
the more severe the reaction.
No crowding effects were observed in single species infections
of E. lageniformis or in concurrent infections with trematodes.
The shelled acanthor larva was found to have four enveloping
membranes.
Data indicates that when the proboscis reaches a certain
length and width, it does not increase in size, although the neck and
trunk of the worm do increase in size.